Gas turbine engine axial stator compressor

ABSTRACT

The invention relates to an axial compressor stator for a gas turbine, said stator comprising a rigid, external, annular frame ( 2 ), furthermore axially juxtaposed rings ( 4   a,    4   b,    4   c ) configured within the frame ( 2 ) and bearing annuli of stationary vanes ( 5 ), said rings being constituted by arcuate segments ( 7 ) affixed to the frame, the inside walls of said arcuate segments externally defining the aerodynamic conduit for the compressed gaseous fluid, and this invention is characterized in that the arcuate segments ( 2 ) are brazed segments consisting of a honeycomb component ( 8 ) sandwiched between an inner sheetmetal ( 10 ) bounding the aerodynamic conduit and an outer sheetmetal ( 9 ), and in that the connection to the frame ( 2 ) is solely implemented by the outer sheetmetal ( 9 ).

[0001] The present invention relates to gas turbine compressors and inparticular to turbojet engine compressors.

[0002] More specifically, it relates to an axial compressor statorcomprising a rigid, external annular frame and axially juxtaposed ringswhich are configured radially inside the frame and which supportstationary annuli of vanes running radially inward, these annuliincluding arcuate segments affixed to the frame by appropriate fasteningmeans and externally defining the compressed-gasses' aerodynamicconduit.

[0003] In general the arcuate segments comprise an inside wall boundingthe aerodynamic conduit and radial ribs pointing outward and restingagainst the external annular frame, the ribs configured with bases toaffix by means of bolts the arcuate segments on the frame. Thestationary vanes are affixed in an orifice in the inner wall.

[0004] The compressed gases of a turbojet engine high-pressurecompressor are hot. The inside walls of the arcuate segments are indirect contact with the hot gases and therefore expand, providingadditional play between rotor and stator. Conductive heat transfer bymeans of the ribs and bolts takes place between the inside wall and theannular frame. The rise in frame temperature entails an increase indisplacement directly affecting the play between rotor and stator. Theconventional remedy includes cooling the assembly by tapping a coolergas flow from a region upstream of the compressor, which results,however, in an overall degradation of gas turbine engine efficiency.

[0005] Accordingly and in a first goal, the present invention proposes acompressor stator wherein the heat transfer between aerodynamic flowconduit and the frame is substantially reduced.

[0006] The second goal of the present invention is a compressor statorproviding improved dynamic behavior of the arcuate segments.

[0007] The present invention attains these goals in that the arcuatesegments are brazed segments defined by a honeycomb component sandwichedbetween an outer sheetmetal and an inner sheetmetal bounding theaerodynamic conduit, and in that the connection to the frame isimplemented solely by the outer sheetmetal.

[0008] Due to this geometry, heat conduction is lowered because theconnection between the hot inner sheetmetal and the outer sheetmetal isimplemented uniquely by the honeycomb component which restricts the sizeof the thermally conducting and contacting surfaces between the hotinside and the cold outside. The temperature of the outer sheetmetal issubstantially lower than that of the inner sheetmetal. This is even morethe case for the external annular frame. Since the brazed arcuatesegments provide a good seal, the air flow in the cavities between theouter and inner sheetmetals is restricted, and, as a result, convectiveheat loss is decreased.

[0009] The airflow which must be tapped upstream to cool the rigid,annular frame may be considerably lowered relative to that of thepresent state of the art.

[0010] Advantageously the outer sheetmetal is affixed by bolts to theframe. Preferably, the outer sheetmetal is affixed by a plurality ofbolts at its downstream end to the frame and at its upstream end.

[0011] This rigid affixation both improves the dynamic behavior of thearcuate segments and permits the inner sheetmetal to expand freely.Consequently, the leakage between upstream and downstream is reduced andcompressor efficiency is increased.

[0012] In another feature of the present invention, the stationary vanesare imbedded both in the inner and in the outer sheetmetals.

[0013] These two sheetmetals are rigidly connected to each other bymeans of the brazed honeycomb component and they are sufficiently apartfrom each other to restrict embedding stresses and to improve vaneassembly shock absorption.

[0014] The honeycomb arcuate segments allow reducing stray leakagebetween downstream and upstream, resulting in higher compressorefficiency.

[0015] Moreover the design is simplified because there no longer is aneed to install additional sealing elements between the cavities and thearcuate segments.

[0016] Other advantages and features of the present invention areelucidated in the illustrative description below and in relation to theattached drawings.

[0017]FIG. 1 is a cross-sectional view of a turbojet engine compressorstator of the invention in a plane along the axis of rotation; and

[0018]FIG. 2 is a perspective view of an arcuate stator segment of thepresent invention.

[0019]FIG. 1 shows a portion of a turbojet-engine compressor statorwhich, inside an external casing defining within it a cold-air flowpath, contains a rigid annular structure 2 that is connected byfrustoconical walls 3 to the external casing, furthermore a plurality ofaxially juxtaposed rings 4 a, 4 b, 4 c that are concentricallyconfigured inside the annular structure 2. Each ring supports an annulusof stationary vanes 5 running radially inward. An omitted rotor flangeis fitted with annuli of moving blades and is configured coaxiallyinside the rings 4 a, 4 b, 4 c, the annuli of moving blades alternatingaxially with the annuli of stationary vanes in the flowpath 6 of the gascompressed by the compressor.

[0020] To mount the stator around the rotor, each ring consists of aplurality of circumferentially juxtaposed arcuate segments 7.

[0021] According to the invention and as shown in FIGS. 1 and 2, eacharcuate segment 7 consists of a honeycomb component 8 sandwiched betweenan outer sheetmetal 9 and an inner sheetmetal 10. The outer sheetmetal 9is fitted at its upstream and downstream ends 11, 12 with a plurality oforifices so that it may be affixed by bolts 14 onto the stationaryannular structure 2.

[0022] It will be understood that bolts 14 are used to connect theupstream end 11 and the downstream end 12 of two axially juxtaposedarcuate segments 7. This particular configuration acts as a seal betweenthe juxtaposed rings 4 a, 4 b, 4 c and runs perpendicularly to the outersheetmetals 9.

[0023] As shown in the drawings, the upstream and downstream ends 11, 12of the outer sheetmetal 9 bulge outward in order for the outersheetmetal 9 and the rigid annular frame 2 to touch each other only asfar as the upstream and downstream ends 11, 12 of the outer sheetmetal9, whereby the conductive heat transfers between the outer sheetmetal 9and the annular frame 2 shall be reduced as much as possible.

[0024] The honeycomb component 8, the outer sheetmetal 9 and the innersheetmetal 10 are brazed to each other. The cross-section of thewalls/partitions constituting the honeycomb component 8 is small so asto minimize conductive heat transfer through the honeycomb component 8between the inner wall 10 and the outer wall 9. Moreover thewalls/partitions constituting the honeycomb component 8, together withthe outer and inner sheetmetals 9, 10, constitute a plurality of nearlysealed cavities which restrict air flow through the honeycomb componentfrom downstream to upstream, and in turn, also restrict convective heattransfer between the inner sheetmetal 10 and the outer sheetmetal 9. Theinner sheetmetal 10 outwardly bounds the hot-gas flow path 6, the gasbeing compressed by the compressor. Such gases are at elevatedtemperatures and the temperature of the inner wall 10 also is elevated.

[0025] Due to the honeycomb component 8 and to the space between theouter sheetmetal 9 and the annular frame 2 outside its upstream anddownstream ends 11, 12, the conductive heat transfer between the innersheetmetal 10 and the outer sheetmetal 9, and between the outersheetmetal 9 and the annular frame 2 is considerably decreased.

[0026] The inner sheetmetal 10 therefore may freely expand withouthampering the dynamic behavior of the arcuate segments 7. It will beunderstood that the upstream and downstream ends of the innersheetmetals of adjacent sectors merely abut one another in order toconstitute the outer wall of aerodynamic conduit of the hot gas flowpath 6. The design is thus simplified because sealing elements are notrequired in these zones, the sealing of the annuli 7 being maintained bythe honeycomb component 8 and by covering the upstream and downstreamends 11,12 of the outer sheetmetals 9.

[0027] As shown in FIG. 2, the outer ends of the stationary vanes 5 areimbedded in appropriate orifices in the outer and inner sheetmetals 9,10 and in the honeycomb component 8. The outer and inner sheetmetals 9and 10 are rigidly connected by the honeycomb component 8 to each otherand they are sufficiently apart from each other to restrict the stressesdue to imbedding and to improve the mechanical damping of the stationaryvanes 5.

[0028] Aligned orifices 15, 16, 17 may be fitted into the innersheetmetal to tap an air flow F1, for instance to cool turbineblades/vanes.

[0029] The inside ends of the stationary vanes 5 of an arcuate segment 7are affixed in conventional manner on a collar 18.

We claim:
 1. An axial compressor stator for a gas turbine, comprising anouter, rigid, annular frame (2), axially juxtaposed rings (4 a, 4 b, 4c) which are configured inside the frame (2) and which support annuli ofstationary vanes (5), said rings consisting of arcuate segments (7)affixed to the frame (2), the inside walls of said segments (7)externally defining the aerodynamic conduit for the compressed gasfluid, characterized in that the arcuate segments (7) are brazed arcuatesegments constituted by a honeycomb component (8) sandwiched between aninner sheetmetal (10) bounding the aerodynamic conduit and an outersheetmetal (9), and in that the connection with the frame (2) is solelyimplemented by the outer sheetmetal (9).
 2. Compressor stator as claimedin claim 1, characterized in that the outer sheetmetal (9) is affixed bya plurality of bolts (14) to the frame (2).
 3. Compressor stator asclaimed in claim 2, characterized in that each outer sheetmetal (9) isaffixed by a plurality of bolts (14) at its downstream end (12) and atits upstream end (11) to the frame (2).
 4. Compressor stator as claimedin claim 3, characterized in that the outer sheetmetal (9) is spacedapart from the frame (2) outside is upstream ends (11) and itsdownstream ends (12).
 5. Compressor stator as claimed in one of claims 1through 4, characterized in that the stationary vanes (5) are imbeddedinto the inner sheetmetal (10) and into the outer sheetmetal (9).